Question

Ralph is painting the barn below, including the sides and roof.  He wants to know how much paint to purchase. 

Answer 1

PART A

The barn is constructed by the following 2D shapes

Two triangles of height = 4' and base = 20'
Area = 2 × (0.5×4×20) = 80

Two rectangles of length = 20' and width = 15'
Area = 2 × 20 × 15 = 600

Two rectangles of length = 45' and width = 15'
Area = 2 × 45' × 15' = 1350

One base of length = 45' and width = 15'
Area = 45 × 15 = 675

Two rectangles on each on one side of the roof. We have the length = 45'  but not the width. We can work out the width by using Pythagoras theorem

w² = 4² + 10²
w² = 16 + 100
w² = 116
w = √116 = 10.77

Area of the two rectangles on the roof part is = 2 ×10.77 × 45 = 969.33

Total area to paint = 969.33+675+1350+600+80 = 3674.33 ≈ 3700 (to the nearest hundreth)


PART B

Numbers of paint cans needed = 3700 ÷ 57 = 64.9 ≈ 65 cans

PART C

Total cost of paint = 65 × 23.50 = $1527.50

PART D

The barn is constructed by a cuboid and a rectangular prism

V of cuboid = length × width × height
V of cuboid = 20 × 45 × 15
V of cuboid = 13500

V of triangular prism = Area of cross section × depth
V = [0.5×4×20] × 45
V = 1800

Total volume = 1800 + 13500 = 15300